Original study - ZZI 02/2016

The influence of various implant types on peri-implant bone loss – a retrospective radiological evaluation

A comparison of two-piece DENTSPLY Friadent products and one-piece Frialoc/Xive-TG implants showed that the latter exhibited significantly fewer signs of bone loss (p < 0.05) (fig. 10). However, the one-piece Frialoc/Xive-TG implants were placed exclusively in edentulous lowers, in accordance with the Ledermann principle [18]. Comparison of the results for the specific implant types in the upper and lower jaw revealed a similar pattern. However, the bone loss values for the lower jaw were noticeably lower than for the upper.

Augmentation procedures

A similar picture emerged when the implant type was examined for the effectiveness of augmentation. Although augmentation around Astra Tech Dental implants did lead to increased bone loss, it was only half as much as occurred around the Camlog and DENTSPLY Friadent products (fig. 11). Without augmentation, almost no loss was detected around Astra Tech implants. Significantly more bone loss was discovered around DENTSPLY Friadent implants, and even more around Camlog implants.

Discussion

Although follow-up studies covering up to 11 years are available for various implant systems, data for follow-ups of more than 11 years are rare [26]. The data presented in this article represent a large cross section of patients treated in one practice over a period of almost 18 years.

When looking at the bone loss irrespective of subgroups, mean bone loss of 1.2 mm was noted within the first year, 1.3 mm after 2 years, and 1.8 mm at the end of the observation period.

Taking into account the methodological limitations of the radiological measurements [14], these values exceed one of the generally accepted success criteria for butt joint implants, namely, bone loss not exceeding 1.5 mm in the first year and no more than 0.2 mm in subsequent years [1].

Most studies addressing the success rates of upper compared to lower implants have shown higher success rates in the lower jaw [26]. Along with bone quality, bone volume and different methods of preparation appear to influence implant success. Very few studies have indicated comparable bone loss in both the upper and lower jaws [11]. Loss rates in the present study were significantly higher in the upper jaw than in the lower jaw, irrespective of the factors examined.

The implant/abutment connector geometry appears to influence the development of marginal bone. Conical implant connections have been shown to be superior to flat ones due to their intrinsic platform switching [16]. The differences have partly been attributed to conical systems entrapping bacteria in the implant lumen and thus preventing inflammation. Another explanation for the reduced bone loss due to conical connections is that they are subjected to fewer micromovements. According to this explanation, reduced bone loss could be due to reduced load transmission and hence fewer irritations under loading in the implant area [20, 29]. In transgingival implant systems, the highest rates of remodeling occur 4 weeks after implant placement, while in two-piece systems, these rates occur 4 weeks after abutment placement.

Regardless of whether they were placed in the upper or lower jaw, the conical implant systems (ASTRA Tech implants, Conelog implants) examined in the present study showed significantly less bone loss than the butt joint systems (Camlog, Frialit/XiVE) and/or one-piece systems (Frialoc/XiVE TG). Whether these observations can be attributed to one of the explanations just discussed cannot be answered conclusively from the parameters examined here. However, as conical and one-piece connections achieve better results than butt joint connections, regardless of jaw; this suggests that the conical connection significantly influences peri-implant bone levels. These results correspond to those of Krebs et al. [17].

The impact of prosthetic restoration is another interesting factor because a distinction is usually made between bone loss at early and later stages once the implants have been loaded prosthetically [5]. In the present study, bone loss was lowest with implants placed for single crowns, ensuring that existing superstructures continue to function, increasing the number of existing abutments or restoring edentulous lower jaws, while it was significantly higher for those used for supporting bridges or restoring edentulous uppers.

To examine the role of implant length, another recent review compared short (< 10 mm long) implants placed for supporting fixed restorations with standard length implants (? 10 mm) [24]. The data of the 5 studies included in this review were subjected to a meta-analysis to assess the impact of the independent variable of implant length on median marginal bone loss. No significant differences in terms of marginal bone loss were found between the 2 subgroups. However, the authors pointed out that most of the studies did not include long-term data and were very heterogeneous. This may explain the significantly better performance of short (? 9 mm long) implants in the present study. Moreover, 119 of the 168 implants which were < 9 mm long in the present study were Astra or Conelog implants that experienced hardly any bone loss. Additionally the review article revealed a significant dependence of bone loss on implant-abutment connections, with internal connections judged to be superior to external connections.

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